1. Field of the Invention
The present invention relates to a method for preparing a catalyst for polymerization of aliphatic polycarbonates and a method for polymerizing aliphatic polycarbonates using the catalyst, and more particularly, to a method for preparing a catalyst for polymerization of an aliphatic polycarbonate exhibiting high catalyst activity.
2. Background of the Invention
Carbon dioxide from industrial activities, among atmospheric pollutants, has been known as one reason for climatic change according to UNFCCC, so various studies to reduce the amount of carbon dioxide produced have been undertaken all around the world. Therefore, in order to protect the environment and to use carbon dioxide, a method in which an epoxide reacts with carbon dioxide as a carbon source in the presence of a zinc-included catalyst to prepare an aliphatic polycarbonate has attracted attention.
The aliphatic polycarbonate is able to form a film or a particle, and has uses in many areas such as for ceramic binders, evaporation mold, and adhesives. However, this method has a low yield because of low carbon dioxide reactivity. Accordingly, it is difficult to use industrially, so it is required to prepare a catalyst exhibiting high efficiency for increasing the yield of the aliphatic polycarbonate.
Inoue teaches a method of polycarbonate production from carbon dioxide and epoxide in U.S. Pat. No. 3,585,168.
The Inoue catalyst system was prepared by the reaction of a diethylzinc catalyst with materials containing active hydrogen compounds, e.g., water, dicarboxylic acid, or dihydric phenols, and the typical catalyst productivities ranged from 2.0 to 10.0 grams of polymer per gram of catalyst used. The catalyst has shortcomings associated with use and storage, because of stability and sensitivity to moisture and to other catalyst poisons, and it has a low yield, so it has been required to study other catalyst systems.
Zinc dicarboxylic acid esters (Polymer J. 13(4), 407(1981)) reported by Soga have also been described as effective catalysts for copolymerization of carbon dioxide and propylene oxide, and since these are stable materials with none of the handling problems associated with diethylzinc, they represent interesting candidates for a practical commercial catalyst system.
Motika (U.S. Pat. No. 5,026,676) teaches a method for preparing zinc dicarboxylic acid ester in which zinc oxide reacts with dicarboxylic acid in the presence of an organic solvent. Glutaric acid and adipic acid produced catalysts with higher activity than the known zinc dicarboxylic acid ester catalysts, and the catalyst production is about 2 to 26 grams of the aliphatic polycarbonate per gram of catalyst.
It has been reported that zinc dicarboxylic acid ester can be prepared by using various zinc precursors and high crystallinity increases yield per gram of catalyst (Ree. et al. J. Polym. Sci: Part A: Polym. Chem. 37, 1863 (1999)).